U.S. patent number 7,104,497 [Application Number 10/471,458] was granted by the patent office on 2006-09-12 for method of synchronizing fin fold-out on a fin-stabilized artillery shell, and an artillery shell designed in accordance therewith.
This patent grant is currently assigned to BAE Systems Bofors AB. Invention is credited to Stig Johnsson.
United States Patent |
7,104,497 |
Johnsson |
September 12, 2006 |
Method of synchronizing fin fold-out on a fin-stabilized artillery
shell, and an artillery shell designed in accordance therewith
Abstract
This disclosure relates to a method of limiting the yawing
motion on the trajectory of an artillery shell during the firing
phase using a sliding driving band and completely folded-in guide
fins. The shell is converted as soon as possible outside the mouth
of the barrel of the firing piece by fold-out of the guide fins
into a fin-stabilized artillery shell. Any form of non-uniform fin
fold-out is avoided by virtue of all the guide fins being
interconnected to form a system which gives all the fins the same
movement pattern and the same fold-out speed in each phase of fin
fold-out. This disclosure also includes a shell in which
synchronization of fin fold-out includes a rotatable control ring
that is arranged around the axis of the shell and is connected to
the rotation spindles of all the fins.
Inventors: |
Johnsson; Stig (Karlskoga,
SE) |
Assignee: |
BAE Systems Bofors AB
(Karlskoga, SE)
|
Family
ID: |
20283429 |
Appl.
No.: |
10/471,458 |
Filed: |
March 20, 2002 |
PCT
Filed: |
March 20, 2002 |
PCT No.: |
PCT/SE02/00550 |
371(c)(1),(2),(4) Date: |
April 27, 2005 |
PCT
Pub. No.: |
WO02/079716 |
PCT
Pub. Date: |
October 10, 2002 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050229806 A1 |
Oct 20, 2005 |
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Foreign Application Priority Data
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Mar 20, 2001 [SE] |
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0100956 |
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Current U.S.
Class: |
244/3.29 |
Current CPC
Class: |
F42B
10/16 (20130101); F42B 10/14 (20130101) |
Current International
Class: |
F42B
15/01 (20060101) |
Field of
Search: |
;244/3.1,3.21,3.23,3.24,3.29,3.27 ;114/23,144R-172 ;102/348
;318/580-589 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0448437 |
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Sep 1991 |
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EP |
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WO-98/43037 |
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Oct 1998 |
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WO |
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Other References
"Driving Bands";
www.absoluteastronomy.com/encyclopedia/d/dr/driving.sub.--band.htm.
cited by examiner .
"Base bleed." Wikipedia, The Free Encyclopedia. Apr. 13, 2006,
23:52 UTC. May 1, 2006, 17:11
<http://en.wikipedia.org/w/index.php?title=Base.sub.--bleed&oldid=4834-
5930>. cited by examiner .
"Artillery." Wikipedia, The Free Encyclopedia. May 1, 2006, 00:19
UTC. May 1, 2006, 17:12
<http://en.wikipedia.org/w/index.php?title=Artillery&oldid=50968069>-
;. cited by examiner.
|
Primary Examiner: Palo; Frank
Assistant Examiner: Holzen; S. A.
Attorney, Agent or Firm: Connolly Bove Lodge & Hutz LLP
Hume; Larry J.
Claims
I claim:
1. An artillery shell suitable for firing from a rifled barrel, the
shell comprising: a sliding driving band; foldable stabilizing fins
which are folded out after firing of the shell and which convert
the shell into a fin-stabilized projectile; a control ring
rotatably arranged around an exhaust opening of a base bleed unit
which is in a same part of the shell as the fins, said fins being
mounted concentrically outside the base-bleed unit, wherein the
control ring synchronizes and makes uniform the fold out movements
of the foldable stabilizing fins.
2. The artillery shell of claim 1, wherein each of the fins have an
associated active area which is rotatably mounted around an
associated spindle arranged essentially in a longitudinal direction
of the shell and around which the associated active area rotates
from a first, folded-in position, in which said associated active
area lies essentially tangential to a shell body and a free outer
end thereof is curved in towards the shell body, to a second,
folded-out position, in which the associated active area extends
essentially radially out from a surface of the shell body, wherein
the movement transmission means comprises at least one control ring
arranged rotatably round the longitudinal axis of the shell and is
connected to spindles of all of the fins so as to control the
movement of each of the fins.
3. The artillery shell of claim 2, wherein the at least one control
ring has an external toothing while the spindle of each fin has, at
a respective place of connection to the control ring, corresponding
toothing in engagement with the teeth of the control ring.
4. The artillery shell of claim 2, wherein the at least one control
ring comprises external toothing, and wherein the rotation spindle
of each fin is arranged so as to make contact with the control
ring.
5. The artillery shell of claim 1, wherein the movement
transmission means is located around an exhaust opening of a base
bleed unit which is arranged in a same part of the shell as the
fins, said fins being mounted concentrically outside the base-bleed
unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a National Stage Entry of PCT/SE02/00550 filed
on Mar. 20, 2002, which claims priority under 35 U.S.C. .sctn.119
to Swedish Application 0100956-2, filed on Mar. 20, 2001.
BACKGROUND OF THE INVENTION
The present invention relates to a method of synchronizing fin
fold-out on a long-range artillery shell which is fin-stabilized on
its trajectory towards the target and is intended to be fired from
a rifled barrel and is to this end provided with a sliding driving
band as the main contact surface against the inside of the barrel
and also with a number of stabilizing fins which can be folded out
after the shell has left the barrel. The purpose of the sliding
driving band is to allow the shell, in spite of the rifling of the
barrel, to leave the latter with only low rotation or no rotation
at all.
It is particularly characteristic of the method and the shell
according to the invention that the stabilizing fins of the shell
are interconnected by specially designed movement transmission
means which bring about uniform fold-out of all the fins
irrespective of how these are loaded during the fold-out phase
itself. Even if the shell should leave the barrel entirely without
rotation, the fins arranged around the shell will nevertheless be
loaded differently during the fold-out phase by the forces
generated by the air flowing past. This is because it has proved to
be impossible to avoid any type of shell being subjected to a
certain conical yawing motion on its trajectory, and this yawing
motion begins immediately after the shell has left the mouth of the
barrel.
The reason why an artillery shell is fin-stabilized instead of
being rotation-stabilized may be, for example, that it is desirable
to make it guidable on its way towards the target, and it is
considerably easier to correct the course of a fin-stabilized shell
than of a rotation-stabilized shell, and this is the case
irrespective of whether the course correction concerned is intended
to be performed by impulse motors, steering rudders or in another
manner.
It is a requirement of the shell according to the invention that it
should be capable of being given an extra long range. A method used
increasingly in recent years of achieving extremely long ranges
even in older barrel-type artillery is the base-bleed technique,
which is used in order to eliminate the turbulence and negative
pressure which are formed behind the shells flying through the
atmosphere and have a braking effect on the shells and shorten
their flying distance. The base-bleed technique is based on
arranging a combustion chamber in the rear part of the shell, which
chamber is filled with a slow-burning pyrotechnic composition
which, while it burns, produces combustion gases which are allowed,
in a predetermined quantity, to flow out through an opening in the
rear end wall of the shell and there eliminate and fill the
abovementioned braking turbulence and negative pressure behind the
shell.
When a shell is to be provided with both a base-bleed unit and
stabilizing fins, however, it is easy for positioning problems to
arise, because the base-bleed unit definitely has to be arranged in
the rear part of the shell with at least one gas outflow opening in
the rear end wall of the shell, while the fins too ought to be
positioned in the rear body of the shell as far away as possible
from the centre of gravity of the shell, that is to say fins and
base-bleed unit should preferably be arranged within the same part
of the shell. An additional problem is that, in order to allow
firing of the shell from a rifled barrel, the fins must be fully
folded in inside the minimum diameter of the barrel during firing,
at the same time as they must not occupy too great a volume either
and thus prevent the use of this space for other purposes such as,
therefore, the base-bleed unit or payload.
In a known type of fold-in fin, which takes up little space and can
be designed so that, in the folded-in position, the fins can share
the rearmost part of the shell with a base-bleed unit, each fin
consists of a plate which is fixed to a rotatable spindle arranged
in the longitudinal direction of the shell and which, in the
folded-out position, will constitute the active area of the fin
and, in the folded-in position, is rotated in towards the shell
body about its spindle, and is in this position curved in towards
the shell body and, until the desired fold-out time, is retained in
this position by a protective cover or equivalent. Previously, such
fins were designed with a curved shape following the shell body and
they retained this shape in the folded-out position as well, but,
in recent years, elastically deformable materials have become
available, which have such a good shape memory that it is now
possible to produce fins which, even after years of incurvation in
the folded-in position, essentially recover their original shape.
It has therefore become possible to use these materials to produce
fins which, as soon as they are given the opportunity, tend to
recover the shape they were originally given, and this may have
been entirely plane or slightly propeller-shaped or designed in
another way so as to be provided with a limited angle of attack
relative to the air rushing past. One way, which is relatively
simple in terms of manufacture in this context, of giving the fins
the desired angle of attack is to provide them with a sharp or
gently curved dog-ear design or a few degrees of propeller twist.
All these types of guide fins are presupposed at the same time to
have a radial main direction seen in the cross-sectional direction
of the shell. The angles of action relative to the air rushing past
the shell which are chiefly of interest in the case of the guide
fins for fin-stabilized shells are usually of the order of 1
2.degree., and corresponding angles of action can of course also be
brought about by means of axes of rotation for folding in and
folding out the fins which are inclined relative to the
longitudinal axis of the shell, but this would as a rule involve
more expensive overall solutions.
As an example of the state of the art, WO 98/43037 may be
mentioned, in which a fin-stabilized artillery shell with fold-out
stabilizing fins of the type described above is disclosed.
SUMMARY OF THE INVENTION
In the introduction, it was stated that every type of artillery
shell is already subjected to a certain form of conical yawing
motion on the trajectory immediately after it has left the mouth of
the barrel and that this results in fold-out fins arranged on the
shell being subjected to different degrees of loading by the
relative wind of the surrounding air, which can moreover, to some
extent, be from different directions. In brief, this means that the
various fins on a fin-stabilized artillery shell will be loaded
differently during the fold-out phase itself. In the case of shells
provided with sliding driving bands, the centrifugal force acting
on the fins is of little importance for fin fold-out. Instead, the
majority of the fold-out force comes from the straightening force
of the fin material, that is to say the force which is generated
when the elastic deformation of the fin material returns to the
original shape the fin was once given. In their folded-in position,
elastically deformed fins of the type concerned here will quite
simply spread out by virtue of their own built-in force but, in
spite of this, the fold-out function cannot be left entirely to
this mechanical energy development, inter alia because it is
clearly most marked during the initial introductory phase of
fold-out. For this reason, the fins are normally also provided in
the previously indicated manner with a small angle of attack
relative to the flying direction of the shell, so that the forces
of the air will, above all in the final stage of fold-out, make
their contribution to the requisite fin fold-out force. However, on
account of the yawing motion of the shell, the air forces may vary
quite considerably in strength and direction between the different
sides of the shell because the relative wind against the shell is
dependent on the yawing motion of the shell which begins directly
outside the mouth of the barrel. A fin on one side of the shell
could therefore, if it were able to define its own fold-out speed,
have such a high fold-out speed that its strength is put at risk,
while a fin on another side of the shell could at the same time
have such a low fold-out speed that it does not completely reach
its intended radial position.
Accordingly, the object of the present invention is to eliminate,
in a reliable manner, the effects of an otherwise readily occurring
incomplete fin fold-out, and this is achieved by fold-out of the
fins in relation to one another being synchronized using means
adapted thereto. According to the invention, the fins are therefore
to be interconnected in such a manner in relation to one another
that they are folded out at the same speed. The invention therefore
concerns a method of forcing the fins most heavily loaded in the
fold-out direction to share the fold-out force acting on them with
fins which are more lightly loaded in the fold-out direction at the
same time as the latter are to force the more heavily loaded fins
to slow down their fold-out speed and thus also to reduce the risk
of them being overloaded. The basic principle of the invention is
therefore that all the fins are to be connected by means of a
common fin fold-out control or synchronizing arrangement which is
to be designed in such a manner that it gives all the fins a
simultaneously initiated uniform fold-out at the same speed from
their initial folded-in position with that part of the fin blade or
the active area of the fin which lies closest to the spindle
extending tangentially to the immediately adjacent outer side of
the shell into a folded-out position in which the fin blades are
angled at in principle 90.degree. relative to the folded-in
position, in which position the fin blades or the active areas of
the fins extend radially out from the shell body. The invention
also includes the fact that the fins should, via the synchronizing
arrangement, help one another with fold-out or alternatively brake
one another as required. A direct drive function is therefore, at
least in the first place, not intended to be included in the
system. An essential part of fin fold-out is also that the fin
plates which constitute the active areas of the fins recover
elastically from their incurvation towards the shell body to the
finally intended shape they were once given. Another advantage of
the invention is that, in an especially preferred embodiment, it
requires very limited extra space and by virtue of this makes it
possible to arrange both the fold-out fins and a base-bleed unit
within the same part of the shell.
The invention therefore provides a method and an arrangement which
guarantee that the fold-out fins on an artillery shell with a
sliding driving band fired from a rifled barrel achieve their
completely folded-out and locked end position. It is characteristic
of the method and the arrangement according to the invention in
this connection that any form of non-uniform fin fold-out and
associated negative influence on the flight of the shell will be
avoided by virtue of all the guide fins being interconnected by
means adapted thereto to form a system which, during the fold-out
phase, gives the fins a synchronized movement pattern with
simultaneous and uniform fold-out movements.
In order to make it possible to perform such a synchronized fin
fold-out function, we have introduced a movement transmission means
which connects all the rotation spindles around which the fins
have, during the firing phase, been curved in towards the shell
body, in which position they have been retained by a special
protective cover from the completion of the shell during
manufacture until it leaves the mouth of the barrel. When the shell
leaves the mouth of the barrel, the protective cover is torn away
from the shell by an inner powder gas pressure which, during the
firing phase, is allowed to leak into the cover and which, inside
the barrel, is balanced by the powder gas pressure behind the
shell. This is because, when the shell leaves the barrel, this
counterpressure ceases very rapidly and, by dimensioning the gas
supply to the cover so that it is not possible for its inner
overpressure to be eliminated at the same rate as the abrupt
reduction in pressure behind the shell takes place, the cover will
be thrown off.
As soon as the protective cover has been removed, fin fold-out will
begin and, as the method and the arrangement according to the
invention are primarily intended for use on shells with sliding
driving bands, there is only at the very most a weak centrifugal
force available to assist fin fold-out. The majority of the force
necessary for fin fold-out therefore has to be obtained, as already
mentioned, from the straightening force built into the fins and
also, to some extent, from the relative wind force against the fins
of the passing air. The object of the method and the arrangement
according to the invention is therefore to even out this
non-uniformity and to give all the fins the same fold-out
speed.
According to an especially preferred embodiment, the main means of
synchronizing the fin fold-out function consists of a control ring
which is arranged concentrically around the longitudinal axis of
the shell close to its outer wall, can rotate in a groove adapted
thereto and connects the various fin spindles and gives these and
the active areas of the fins identical movement patterns. In its
most developed form, the outer surface of the control ring is
designed as a toothed ring and each fin spindle is in turn provided
with a corresponding toothed segment covering at least a quarter of
a turn. Under certain circumstances, it would probably be possible
to replace the toothing with low-cost variants in the form of
knurling or another friction-increasing treatment of the outer
surface of the control ring and the rotation spindles of the fins.
Another possible but, because it would result in so many small
parts, less practical solution would be to use a number of links
which interconnect cranks rigidly connected to respective
spindles.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is defined in greater detail in the patent claims
below and will moreover be described in somewhat greater detail in
connection with accompanying figures, in which
FIG. 1 shows an oblique projection of an artillery shell while
FIG. 2 shows a longitudinal section through the rear part of the
shell,
FIG. 3 shows the section III--III in FIG. 2 with the fins folded in
and covered by a protective cover while
FIG. 4 shows the section III--III in FIG. 2 but with the fins
folded out, and
FIG. 5 shows a detail from FIG. 4 while
FIG. 6 shows the rear part of the shell according to FIG. 2 but in
an oblique projection.
DETAILED DESCRIPTION OF THE INVENTION
The shell shown in an oblique projection in FIG. 1 represents an
example of how a shell designed according to the invention may
appear on its way towards the target. The shell in question
consists of a shell body 1 provided with a groove for a sliding
driving band 2 which has already been lost, a number of folded-out
fins 3 which are attached to the rear portion 4 of the shell, the
connection of which to the shell body 1 is indicated by the join 5.
At the front end of the shell, there are four canard rudders 6a, 6b
and 7a, 7b which can likewise be folded out and are moreover
guidable. All the fins and rudders are designed in such a manner
that they can be kept folded in during the firing phase.
FIG. 2 shows in greater detail how the rear portion 4 is designed.
This portion accordingly comprises an inner cavity 8, in which a
base-bleed charge 9 is arranged. There is also an initiator 10 for
the base-bleed charge and a support dome 12 arranged around the
outlet 11 thereof. Each of the fins 3 is attached to a rotatable
spindle 13 aligned essentially in the longitudinal direction of the
shell. Each such spindle has a bearing point 14 and, respectively,
15 at each end. The active areas of the fins, which consist of
plane plates as in FIGS. 2 6 in the folded-out position, have been
given the general designation 16.
In their folded-in position, the active areas 16 of the fins, which
can be seen more clearly in FIG. 3, are on the one hand folded down
a quarter of a turn around their respective spindles 13 towards the
rear body 4 of the shell so that, in the region of their respective
spindles 13, they extend essentially tangentially along the rear
body 4, and on the other hand curved in at their respective free
outer end along this body and moreover covered by a protective
cover 17 which is removed as soon as the shell has left the mouth
of the barrel.
In order for it to be possible to bring about the synchronization
of fold-out of the fins 16 which is characteristic of the
invention, the spindles 13 of the fins are, somewhere along their
length, in this case at one of their ends, designed with toothed
arcs or toothed segments 18 which in turn are all in engagement
with an externally toothed control ring 19 characteristic of the
invention, which, in a groove 20 adapted thereto inside the rear
body 4 close to its outer wall, runs concentrically around the
central outlet 21 of the rear body 4 for the base-bleed charge.
Until and when the shell leaves the barrel from which it is fired,
the fins will therefore be covered by the cover 17 which, by
interaction between powder gases penetrating into the cover and the
vacuum directly outside the mouth of the barrel, is pulled off,
whereupon fin fold-out begins immediately. By virtue of the fact
that the spindles 13 of all the fins 16, via the toothed arcs 18
and then in turn by the externally toothed control ring or
synchronizing means, are interconnected to form a continuous
system, all the fins will be folded out at the same speed.
As can be seen from FIGS. 3 and 5 in particular, we have, in the
case illustrated, selected a tooth size which, with four teeth for
each toothed arc 18 on the spindle 13 of each fin 16, gives a
fold-out movement corresponding to a quarter of a turn for the
active area 16 of the fin.
* * * * *
References